Parasitic protozoal infections are responsible for a wide variety of diseases of medical and veterinary importance, including malaria in man and various coccidioses in birds, fish and mammals. Many of the diseases are life-threatening to the host and cause considerable economic loss in animal husbandry, such as diseases caused by infection by species of Eimeria, Theileria, Babesia, Cryptosporidium, Toxoplasma (such as Toxoplasma brucei, African sleeping sickness and Toxoplasma cruzi, Chagas disease) and Plasmodium (such as Plasmodium falciparum), and the Mastigophora such as species of Leishmania (such as Leishmania donovani). Another parasitic organism of increasing concern is Pneumocytis carinii, which can cause an often fatal pneumonia in immunodeficient or immunocompromised hosts, including those infected with HIV.
Malaria is a mosquito-borne disease that, in humans, can be caused by five species of Plasmodium parasite, of which Plasmodium falciparum is the most virulent. In 2013, there were an estimated 128 million of people infected with malaria worldwide and malarial disease was responsible for an estimated 584,000 deaths (90% of them in sub-saharian Africa), young children and pregnant women being the most affected groups. In 2013, malaria killed an estimated 437,000 children under five years of age (WORLD HEALTH ORGANIZATION. (2014). World malaria report. Geneva, Switzerland, World Health Organization).
Resistance to classical treatments and emerging resistance to the current treatment of choice (artemisinins-based combination therapies) reveals the urgent need for new therapeutic agents with novel mechanisms of action (WORLD HEALTH ORGANIZATION. Joint assessment of the response to artemisinin resistance in the greater Mekong sub-region. November 2011-February 2012. Summary report.). In 2010, GSK released details of more than 13,500 chemical compounds that have already shown to inhibit Plasmodium falciparum parasite growth in the phenotypic screening approach (Gamo, F. J. et al. (2010) Thousands of chemical starting points for antimalarial lead identification. Nature 465, 305-310). Molecular structures and descriptions of these compounds were made publicly available in accessible databases under the name of TCAMS (Tres Cantos Antimalarial set) (http://www.ebi.ac.uk/chemblntd).